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Old 04-24-2006, 08:55 PM   #1
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Loud "CLUNK" from rear over sharp bumps

I've been noticing more and more a lound "Clunk" from the rear of the car in the neigborhood (best guess) of the right rear shock tower whenever I go over a sharp bump. I think it's getting worse slowly. I also think I hear a fainter version of this from the left side, but not 100% sure.

Would anyone hazard a guess as to what this might be?

I'm hoping its something simple like a the nut on top of a shock tower working its way loose. Even if it is this "nut", I'm not sure how to tighten it.

Could it be something serious like an engine mount?

The car drives normally and the engine seems to be running well (I'm not sure what a broken engine mount might sound like).

I was poking around and when I open the top so that the metal cover that raises 45 degrees to let the roof down [gee, what's this called?] is open, I see two big bolts under it in the same channel as the rear center stop light. On top of these two big bolts are two others things that look like caps. The "caps" are about the same size as the bolts under them. The right cap was slightly loose (only finger tight). Are the big bolts under the "caps" by any chance the the things that I can tighten to lock down whatever it is that is making that "CLUNK"? Are the "caps" only supposed to be finger-tight?
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Old 04-27-2006, 10:37 PM   #2
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I had the same problem some months ago and it has been gradually getting worse. If I where to accelerate hard it would make a clunk. I have been told by forum members that it was an engine mount. I did my research and found out that 97-98 Model year boxster engine mounts break. The new ones have a metal plate or something metallic in between rubber. I'm no expert but sounds to me you have my same problem. Also look at shocks and camber plates. I'm going to buy the Boxster Bentley Manual and do an inspection. If its a pain in the behind to fix it I would probably take it to the dealer, but if it something less complicated I'll do it myself

Last edited by BoxsterRS; 04-27-2006 at 10:39 PM.
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Old 04-28-2006, 01:58 AM   #3
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If your clunk is similar to the one I experienced on my Carrera,
check the sway bar links. They tend to loosen and will sound just
like you describe.

I don't recall the proper torque, but just make them "good and
snug."

Let us know if that helps...

- Mark
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Old 04-29-2006, 09:20 AM   #4
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I still have not had a chance to find out what those big bolts are underneath the soft-top cover (they flank the center stop light). But I hand-tightened the "cap" of the right-hand one by about 1/8th of a turn (it was a bit loose) and the clunk has diminished.

I'll have to check into what those bolts are for and how to tighten them.
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Old 04-29-2006, 10:56 AM   #5
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If it's doing it over bumps then its a blown strut, if its doing it when you accelerate hard likely a mount as the motor is flopping around in the bay.

Both are pertty easy to replace and shouldn't run you an arm and leg.
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Old 04-30-2006, 06:39 AM   #6
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Quote:
Originally Posted by socratic
I still have not had a chance to find out what those big bolts are underneath the soft-top cover (they flank the center stop light). But I hand-tightened the "cap" of the right-hand one by about 1/8th of a turn (it was a bit loose) and the clunk has diminished.

I'll have to check into what those bolts are for and how to tighten them.
Hi,

Those are not Bolts. They are the Base (PN# 986 514 251 01) for the Centering Journals (PN# 986 514 253 01) for the Metal Tonneau which raises/lowers, when you operate the Soft Top. They are not necessarily supposed to be tightened down as these provide some of the Height adjustment to the Tonneau so that it matches flush with the rest of the sheetmetal surrounding it when closed. It would have absolutely nothing to do with symptoms you describe in your initial post. Hope this helps...

Happy Motoring!... Jim'99
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Old 04-30-2006, 03:46 PM   #7
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[QUOTE=socratic]I've been noticing more and more a lound "Clunk" from the rear of the car in the neigborhood (best guess) of the right rear shock tower whenever I go over a sharp bump. I think it's getting worse slowly. I also think I hear a fainter version of this from the left side, but not 100% sure.

Would anyone hazard a guess as to what this might be?



Im pretty sure it is the Lower Control arm. ( approximately $250-380, depending on where you get it).
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Old 04-30-2006, 11:41 PM   #8
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Jim, thanks for letting me know what those big bolts near the center brake light are.

Maybe it's wishful thinking but I swear the clunking is less frequent and less severe with the mild finger tightening that I did of the "cap" on the big nut.

Next time I get a chance to get on the hoist I'll see if it's the sway bar bushings or a lower control arm (I'll have to check the manual to see what that is first so that I can look at it).

Fortunately it doesn't seem to be the engine mounts because I did lots of full throttle acceleration runs and no funny noise or effects during the runs.

Also I'm thinking it isn't a strut because the clunk isn't a bottoming out sound, which is quite harsh and the whole car would shake (I think). Also the car handles and rides well and so this should also mean that it isn't a strut.

Maybe I'm throwing you helpful people off due to a bad description of what the sound is like. While it is a "clunk" sound, it sounds if something is loose when I go over some kinds of bumps. But not all kinds of bumps. Driving slowly over speed bumps don't produce the sound. And many sharp bumps (e.g potholes) don't produce the sound. But some kinds of sharp bumps do make something shake in the back. I wonder if it could be a loose muffler or exhaust piece.

Thanks again for the advice so far.
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Old 05-01-2006, 05:05 PM   #9
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I was getting a similar clunk from the passenger side of my 98 Boxster this spring and was worried about it being from the rear passenger side suspension. I first noticed it after taking my hard top off after winter driving. I realized after the a while that the front passenger side of the Tonneau cover had some play in it (where the driver side did not) and that the noise was largely absent with the top down (and possibly cushioning the tonneau cover on that side).

Dealership just adjusted the tonneau cover at my service this week and the clunk is gone.
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Old 05-19-2006, 07:50 PM   #10
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Need same kinda help..

This thread is really interesting: I have a 2000 Boxster and there is a loud deep metallic rattle/rumble coming form the vacinity of the rear driver's side wheel arch. It's only apparent over sharp bumps or potholes much as you decribe but once loose and rattling is apparent over even minor bumps or vibrations until I have left the car stationary for a while. Then it seems to settle until the next big bump.

I just took it to my local main dealer as the 60K service was due - they have looked at this problem twice now for a total of about 8 hours with both technicians at a loss as to what it could be. Not sway bars, everything apparent has been tightened, and they suggested changing both struts to "see if it fixes the noise"! Sorry, but $2K in repairs without a guarantee is not a good option.

Anyone have any further clues as to what this could be? Like I say - it needs a good bump or set of bumps to get the loose rattling/rumbling started and then any vibration there after will set it going again. Not speed related and all shocks feel fine with plenty of motion and bounce in them. Happens roof up or down.

Alternatively - anyone know of a good Boxster mechanic in Orange County with the patience & time to figure such a problem out? The main dealer guys are all about throughput and get frustrated if they can't just change a part or figure something out relatively quickly I guess.

Thanks - any help much appreciated.
MB
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Old 05-19-2006, 08:20 PM   #11
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im pretty sure it is the Rear Control Arm.
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Old 05-19-2006, 11:38 PM   #12
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We had a noise that sounded like something loose in the rear trunk of our '04.

What I found, and was able to fix myself, was a loose strut, the one that raises the metal panel that covers the top when it is down. There is an aluminum plate on each side that rotates with the action of the top, this strut attaches to that plate with a pivot bolt that has a ball / socket type head.

The socket on the end of the strut somehow gripped the ball, and after a couple years of top operation, caused the bolt to unscrew until it fell out. As it finally came out, it must have bent over to the point that the ball popped out of the socket.

The top seemed to work OK. I stopped the action, of the top, at about half stroke so I could see down the side. Then I saw the bolt laying in the bottom of the area and the strut hanging off the back support (the connection to the structure under the panel).

I threaded the bolt back in the aluminum plate which took some care due to the last thread in the aluminum having been pulled out of shape as the bolt broke free. Once I got the bolt in and tightened, the socket on the strut snapped back in place over the ball on the bolt.

The noise went away and hasn't returned. The dealer said they had not found this on any other Boxster.
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